Pressure and temperature responsive mechanism



May 22, 1945. F, c. Mock PRESSURE AND TEMPERATURE lRESPONSIVE! MECHANISMFiled July 12, 1940 2 sheets-sheet 1 1 Il) A INVENTOR May 22, 1945.

Filed July 12, 1940y '2 sheets-sheet 2 ATTORNEI Patented May 22, 1945FUNITED STATES PATENT- orrlc Frank O. Mock, South Bend, Ind., assign'orto Bendix Products Corporation, South Bend, Ind., a corporation ofIndiana Application .my 12,1940, serial no. 345,089

' 3s claims. (ci. 23e-a2) This invention relates to pressure sensitivemechanism, and particularly to corrugated metal bellows of the type usedto control a device (such as a valve or a switch) as a function ofpressure changes either on the interior or on theexterior of thebellows, or as a function of temperature changes to which the unit issubjected, or as a correlated function of both temperature and pressurechanges to accomplishdensity responsiveness. The instant application isa continuation-in-part of'my copending application Serial No. 120,654,filed January 15, 1937.

Devices of this type have been particularly usethe plane of the base, asmay happen by reason of defective manufacture or assembly of the parts,or by displacement thereof in use. the

corrugations are put under undue stress and the bellows will notfunction properly.

It 1s an object of the instant invention to eliminate or reduce`vibration and undue stress in apparatus of this type. so as to improvethe operation and lengthen the life of theapparatus. This Vis done byprovidingldampening means in association with the bellowaand byproviding an ful in carburetors for internal combustion en- 7gines,`particularly aircr'aft engines, to control carburetor elements inresponse to variations in the pressure, temperature, or density of oneci' the working fluids.

Where such a device is used in an installation where it is subjected tovibration, as on an aircraft motor, it is found that its life isshortened because the vibrationsets up sympathetic vibra- I tions in thebellows which fatigue the metal of A the walls until failure occurs byfracture of the walls. Such vibration is particularly destructive whenits frequency equals the natural periodicity of the bellows or aharmonic thereof, and may be of various types. one of its ends fixed toa member which is subject to vibration, and its other end relativelyfree,

. improved universal connection between the bellows and the. controlledmember whereby one may be moved laterally with respect to the otherwithout putting the bellows under undue stress.

A further object of the invention is to provide an improved constructionwhereby apparatus of this type will function ,accurately and dependablyunder exacting requirements. rather than erratically as in devices ofthe prior art.

It is a further object to provide a device which will accuratelymaintain its calibration over long periods of service and will respondto variations in the density of the air surrounding the bellowsVirrespective of whether the change in density results from a change inthetemperature or Assuming the bellows to have the vibration may besimply an alternate lengthening and shortening of the bellows, in whicheach corrugation shares about equally. Secondly, the vibration mayconsist in a swinging motion A of the free end of the bellows about itsilxed end as a pivot. A third type of vibration, which may occur even ifboth endsof the bellows are fixed, consists in waves oi compression' andextension which travel longitudinally of the bellows, so

that, at any given instant, the several corrugations are u'nequallystressed. Two or all of these types of vibration, and other' types notabove described. may of course be present at the same `time in the samebellows.

-A bellows oi' this type usually comprises a ilexible corrugatedcylindrical wall, a base which is relatively fixed, and a relativelyfree'end which is connected to the controlled member, which may be avalve, an electric switch, or-any device capable of being controlled bythe movement of the bellows. The flexible wallmay be elongated orcompressed, or may be :bent intothe arcof a circle, without puttingundue strain on said vwall,

but if the free end is moved transversely ofthe pressure lof thesurrounding air.

Further objects and advantages of the invention will be apparent fromthe following descrip'- with the appended tion, taken in connectiondrawings, `in which:

Figure 1 is a longitudinal section taken through a device embodying theinvention:

Figure 2 is a similar view showing a modiilcation of V'the invention;

Figure 3 is a similanview showing another modication of the invention: 1

Figure 4 is a similarview showing still another 'modification f theinvention: and

Figure 5 isa similar view showing a still further modification oi' theinvention.

'I'he device disclosed in Figure 1 comprises a iiexible metallic bellowsI0 oi the known type'.

secured at its upper end to a base l2 of a relatively Ailxed memberwhich seals the end oi' the bellows.

der zo depending frcm thenxed member 12. The

control member in this case .is shown as a needle V.valve 22 whichcooperates with a fixed valve member 24 to control the flow of iluidthrough an orince in the-latter. The. valve 22 is slidably guided by afixed sleeve 26 which is provided with an annular boss 28 which slidablyengages the interior of cylindrical portion I6. The top of the valve 22isrounded as at 2 3 so as to slidably engage the interior of portion I6.Acompression spring 30 tends to maintain valve 22 off its seat.

The interior of the bellows is partially filled with a body of oil 32 ofsuitable and relatively constant viscosity, a space 33 being left abovethe. oil level to permit the bellows to function. By regulating thevolume of the enclosed space 33 above the oil and the stiffness ofspring 30 the sensitivity or amount of valve movement for given pressurechanges may be conveniently regulated. Furthermore, the sensitivity ofthe bellows to changes in temperature'may be regulated by controllingthe absolute pressure within the bellows at the time of sealing thesame, it being not responsive to temperature changes if the space isentirely evacuated and becoming increasingly responsive to temperaturechanges as the absolute pressure within the bellows is increased. Bycorrelating the volume of this space and-its absolute pressure at thetime of sealing it is possible'to obtain a device which will respondaccurately to changes in air density. irrespective of whether the changeresults from change in air temperature or change in air pressure. Itwill be readily apparent that the bellows will tend to collapse as thespace 33 is evacuated. The ynatural' e1as ticity of the bellows willtend to resist such collapse due to evacuation; however, lif the degreeof evacuation is high it may be necessary to use a compression springwithin the bellows to assist in resisting the collapsing action due tothe evacuation.

If the space 33 above the oil lsiilled with air, it has been found thatthe ivalve'setting or calibration of the unit will change with use asthe oxygen in the air combines with the oil, thus changing the effectiveinternal pressure.

Such a change in the internal pressure also disturbs the correlationbetween the pressure and the temperature responsiveness necessaryfoiaccurate density compensation. By using ,nitrogen within the bellowsit has been found that the unit will maintain its calibration over longperiods of use. Other inert gases having no tendency to combine with theoil and substantially no tendency to dissolve inthe oil may also beused, gases having such characteristics being herein designated vasinert gases. l

It is assumed thatmembers 20, i8, IB, 28,' 22 and 24 were designed to.aline perfectly. with each other, but that defectsof manufacture orassembly, or the stresses occurring in` service, producedthemisalinement shown in Figure 1.

putting undue strains on the bellows," and also prevents vibration of.the types a e discussed, type 2 being prevented by the engagement ofportion `I6 with boss 28, andi types I and 3 being damped out by theoil32, which opposes rapid changes inthe shape of corrngationssuch a`sthe latter two types of vibration involve. If it is declearance betweenthese two members is' made `eciualto or preferably less than theinternal distance between the walls of a convolution, as is best shownin'Figure 3,`the damping effect of the 75 changes in the temperature andpressure there- 80 bellows.

The construction permits such misalinement withouty from the spaceenclosed by the cap 50 to the air oil is materially increased. It willbe readily apparent that the eectiveness in damping ofthis clearancedimension will'vary with changes in the viscosity of the oil used.However. by proper adjustment of viscosity and the clearance any degreeof damping is obtainable.

The' device shown in Figure 2 is generally similar to that justdescribed except as hereinafter noted. Depending from the base I2 is acylin- 10 drical member 34 which has its lower end 36 enlarged to forman annular plunger which cooperates with the body of oil 32 lyingbetween members I6 and the walls of bellows I0 to form `a dashpot whichresists quick movements of contraction and expansion in the bellows.`Here again the adjustment of the clearance between member' 36 andmember III and also between member 33 and memberv I6 will provide any desired degree of damping. Member 34 is provided near its top with ports38 designed to equalize the pressures existing interior and exteriorofmember 34. By controlling the size of ports 33 a limited amount of airor gas damping action `may be obtained. The space 33 above the oil is,as

before, preferably filled with nitrogen or some other inert gas. Forfurther damping of the vibrations in the corrugations of bellows I0 arubber sleeve 39 may be placed outside of the bellows in frictionalrelation to the outer walls of the The sleeve'v 39 is preferably`deformable to permit transverse movement of one end closure platerelative vto the other as is experienced when misalinement is presentbetween the parts of the assembly. It will be` readily apparent that the35 `damping actions obtained by the clearance between member 36 andmembers I0 and IBpby the air port 38, and by they rubber sleeve 33 eachacts independently of the others and is adapted for use either by itself0r in combination vwith one or more of the other arrangements. The

rubber sleeve 39 is lequally applicable for use with the otherembodiments as well. i

Figurev 3 illustrates a further Iembodiment of the invention applied toan internal combustion engine carburetor having an air inlet 40 and acontrol passage 4| 'which may be a fuel passage, an air passage, or mayserve to connect a control diaphragm or the like to a variablevsource ofpressurek su'ch as the engine intake manifold.

The fixed member I2 includes a cylindrical chamber portion 42 to whichthe collapsible bellows lI0 is secured thus forming a chamber having acollapsible lower portion and a non-collapsible. upper portion. Themember I2 is carried by a housing 43 winch isrsupported by a member 44rigidly secured to the carburetor body. Perforations 46, 41 are formedin the member 44 and housing 43 respectively toprovide for circulationof air or other fluid around the'bellows '60 as hereinafter described.Preferably the perforations"46 in the member 44 are covered by gauze 48or the like to'iilter the air. A cylindrical. shell or cap 50 surroundsand encloses the upper portion of housing 43' and is securedy thereto bylockingsnuts as shown. A pipe 52 leads intake orto some other source ofmoderate suction. 'Ihe air or otheriiuid; the' temperature and pressurevariations of which it is desired to com- 7QA pensate for, is drawnthrough ports 43, past the damp vibrations of the bellows.

of, such as might occur 'if the airplanerapidly ascended or descended. Arestriction 53 may be used in pipe 52, if desired, to prevent any unduetransmission of suction to the interior of housing 43 which mightotherwise interfere with the bellows accurately responding to thepressure of the fluid supplied to ports 48.

The cylinder I6 lies closely adjacent to the extension Int extendingthrough the base member '9 I `and secured thereto by cap I 0l.

A vertical passage I I 0 in the extension |06 com.

municates with the free space within the bellows through a plurality ofradial passages I|2 and `one of said passages |I2 communicates withtheinterior of the cylinder |04 through a port ||4 controlled by anadjustable needle valve I6. The

inner part of the corrugations in the bellows to. I

restrict the passage for viiow of oil 32 between adjacent corrugations.Thus the oil 32 serves to It should be noted that the entire collapsibleportion of the enclosed chamber is illled with oil, the air or inert gasspace 33 being conned to the noncollapsible portion, thus permitting theoil to dampthe vibrations in allot the corrugations.

A recess |54. provided in the enlarged head 2| oi I valve 22 slidablyreceives a hollow plunger I55.

A relatively stili' spring 58 urges the rounded head oi' plunger 65against the upper end of cylinder I6 and the head of valve 22 against apassage |||l is provided with a port whichfcommunicates with a duct II8leading to a chamber closed by a diaphragm |22. The other side of thediaphragm is connected through a pipe |24 to a source of the variablepressure which is to be used to actuate the bellows. The bellows 92.

retaining washer 51 and a snap ring 58, the latter being received in agroove inlthe wall of cylinder I6. 'I'he valve 22 is thus preventedfrommovling vertically relative to the cylinder I6 but is permitted, by theclearance between the head of valve 22 and the cylinder- I8, to movetransversely relative thereto if misalinement is present. Misalignmentbetween the valve 22..and the cylinder I8 is thus accommodated inexactly the chamber |20l and interconnecting passages are filled withoil or other liquid of substantially constant viscosity regardless of'temperature changes, thus providing a solid liquid column from thediaphragm |22 to the bellows 92 so that vany variations in pressure inthe pipe |24 will be transmitted through the diaphragm substantiallyundiminished to the bellows.

The cylinder |04 may be closely adjacent the -inner edges of thecorrugations to restrict the -ilow of oil into and out of thecorrugations Ifor damping vibrations. This construction permitsmisalinement and dampsout vibration. In addition the piston 88 andthevari'able port II4 provides a dashpot which permits of obtaining anydesired amount of damping.

It will be readily apparent that the dashpot y piston arrangement in thebellows 92 of Figure 5 enlarged to i'orm an air chamber B6 with the,plate 68. The lower end of the bellows is closed by a plate 10, towhich is secured a plunger 'I2 cornprising a lower disc 14 which slideswithin member B4, and an upper disc 16 which slidably engages a iloatingannular member 18 vheld in `fric tional relationwith the shoulder ofmember 04 by a spring $2, It will thus be seenvthat disc l' is notlimited to the diaphragm type of pressure actuation and would be equallyapplicable in a 'V sealed and partially liquld-illled bellows of thetype disclosed in Figures 1 to 3.

' While lseveral of the embodiments of the invention have been shown/anddescribed in detail, lt is to be understood that the invention is notlimited thereto or votherwise than by the terms of the appended claims.

Iclaim: l. A sensitive element' comprising a -hollow ilexible memberadapted to changevits shape in response to variations in pressureon'opposite sides thereof, means for rigidly mounting one 16 and chamberB6 form an air dashpot which tends to damp out longitudinal vibrationsin the bellows, and that any misalinement between the bellows and theplunger 12 will be taken care of by a pivoting of said plunger aboutdisc 14, m'mber 18 being moved' laterally to accommodate such movement.The plunger 12 slidablyy engages the enlarged head B4 of member 22 toaccommodate misalinement between these two members. ,y A

In the modification of Figure 5. the controlled member ll is connectedthrough a universal connection l1 to one end of a'lever 88 which ispivotally mounted at on an extension ofthe base member 9|. A bellows'92is closed at its upper end by a yplate 94 which is yfixed toor formedintegral with a rod 80. Therod 96 is lpivotally connected at its upperend to the lever Il and terminates at its lower end in a bail 9B whichis secured in a piston 98 by a plug IDO-to form a universal connectiontherewith.- The "lower end oi' the bellows lis closed by a plate |02having an upper cylindrical extensionV y|04 slidably receiving thepiston 99 and a lower tubular end of said member, angularly movablemeans slidable relative to each other longitudinally of the flexiblemember for connecting the opposite end of the member to said one end,and means including a body of liquid inside of said-member to dampvibrations therein.

2. A sensitive element comprising a ilexible tubular. shell, means i'orrigidly mounting one end oi' said shell, means closing the opposite endof said shell, means including a. body of liquid inside o! said shellfor damping vibrations therein, a ball element carried by one of saidmeans, and a guide member carried by the other of said means andengaging said ball element to form a relatively slidable and angularlymovable Joint.

3. A sensitive element comprising a tubular bellows, means for rigidlymounting one end of said bellows. means for closing the other end ofsaid bellows including a tubularfguide portion, a fixed 'guide memberincluding an enlarged head angulariy and longitudinally slidablerelative to said guide portion. and a member to be actuated slidablycarried by said guide member y and engaging said closing means.

4. A sensitive element comprising a tubular bellowsI means for vrigidlymounting one end of said bellows, means for closing the other end ofsaid bellows including a tubularguide portion.

a xed guide member including an enlarged head slidably engaging said,guide portion, a guide sleeve rigidly carried by one of said means, and

a ball element carried by the other of said means and slidably engagingsaid guide sleeve. m

5. A sensitive element comprising a tubular bellows, means for rigidlymounting one end of said bellows, means for nclbsing the other end ofsaid bellows including attubular guide portion, a xed guide memberincluding an enlarged head slidably engaging said guide portion, a guidesleeve rigidly carried by one of said means, and a ball element carriedby the other of said means iblemember and movable relative to the rstand slidably engaging said guide sleeve, said bel-l lows adapted tocontain a body of liquid to damp vibrations thereof.

6. A sensitive element comprising 'a tubular'y bellows, means forclosing the ends of said bellows, said bellows being adapted to containa body of liquid, and an annular plunger carried by one oi' said-meansand projecting into said body of liquid, said plunger being formed withrestricted ports, whereby vibrations of the bellows will be damped.

7. A sensitive element comprising a. tubular bellows, means for closingAthe ends of said bellows, a tubular member carried by one of said meansand lying inside of the bellows, and a plunger carried by the otherl ofsaid means and slidable in said tubular, member to damp vibrations ofthe bellows.

8. A sensitive element comprising a tubular bellows, means for rigidiymounting one end of the bellows, means for closing the other end of saidbellows, a dashpot cylinder carried by one 0f said means, a` piston insaid cylinder and connamed plate, and 'a non-deformable member rigidlyconnected to one of said plates and forming a longitudinally slidableuniversal connection` with the other of saidplates. adjacent said oneend of the flexible member.

14. A sensitive element comprising a hollow 25 stant viscosity iilling apredetermined portion oi said ilexible member and contacting the sidesnected to the ,other of said means, said bellows and cylinder adapted tocontain liquid, and means forming a restricted conection between theinside and the outside of said cylinder.

9. A sensitive element comprising a tubular bellows, means for rigidlymounting one end of said bellows, means for closing the other end ofsaid bellows including a. tubular guide portion, a ilxed guide memberincluding an enlarged head slidably engaging said guide portion, .aguide sleeve rigidly carried by one of said means, a ball elementcarried by the other of said means and `slidably engaging'said guidesleeve, a control'element slidably carried by said guide member, saidcontrol element having a ball shaped end adapted to engage the end 'ofsaid tubular guide portion, and a spring to urge said ball shaped endinto engagement with the tubular guide portion.

10. A sensitive element comprising a-tubular bellows having upper andlowerends, means closing the ends of said bellows, a body of liquid insaid bellows, an annular plunger depending from the upper of said meansand projecting into saidv body of liquid thereby dividing the spaceabovel response to variations in pressure on'DDOsite sides thereof. arelatively iixed base member clos'` inone en'd of said member, arelatively movable .thereof to damp vibrations therein, the remainingportion of the hollow space within said member being subjected to apredetermined degree of evacuation to remove air and its containedchemically active constituents, and a predetermined quantity oftemperature-responsive rinert gas in the evacuated space enclosed vbysaid flexible member to minimize association with or dissolution in thedamping liquid and thereby avoid change in the temperature-responsivecalibration of the device.

15` A sensitive element adapted to control a carburetor element of anaircraft engine in accordance with changes in air density accompanyingchanges in altitude comprising a tubular bellows, means for sealing theends of said bellows, a body of oil filling a, predetermined portion ofthe bellows to damp vibrations therein, and a predetermined quantity oftemperature-responsive gas filling the remainder of said bellows saidgas being of an inert type having a low affinity for and a low factor ofsolubility in the 'damping liquid whereby the gas content of the devicewill ref Y main constantv over longperiods of time to thereby providelasting temperature calibration oi the device. y

16. A pressure responsive device comprising a deformable cylindricalmember, 9, xed plate closing one end of said member, a plate movablerelative to said fixed plate closing the other end of said member, amember fixed to one of said plates and engaging a portion of the otherof said plates to form a. longitudinally slidable and angularly movableconnection'therebetween, a body of liq-I uid partially lling saiddeformable member, and an inert gas iilling the .remainder oi' saiddeform, ablemember.

17. A pressure responsive device comprising' a corrugated metallicmember a ilxed plate closing "one end of said member, a relativelymovable plate f closing the other end of said member, and a deformablecasing enclosing said corrugated member and irictionally en'gaglngthesides thereofj to damp vibrations. f

18. A pressure responsive device comprising a hollow flexible memberadapted to change 'its shape in response to, variations in pressure onopposite sides thereof, a relatively iixed plate closing one end of saidmember, a relatively mov- 2,876,711 able plate closing the other end ofsaid member,

and a deformable sleeve connected to one. of said plates. andsurrounding and f rictionally-engaging the sides of said flexiblemember. y

19. 4A sensitive element comprising a flexible bellows, a pair of platesclosing the ends of said bellows, means forming auniversai connectionbetween said plates permitting longitudinal relative movement of-saidplates, and a deformable sleeve surroundingand frictionally engagingsaid bellows to damp vibrations thereof.

20. A pressure sensitive element comprising a sealed chamber having alower corrugated bellows-like deformable portion and an upperrigid-walled cylindrical non-deformable portion,

a body of clamping liquid completely illling said deformable portion anda gas filled space above said body of liquid, the level of the liquidbeing above the uppermost'corrugation of the bellowslike portion, tothereby dampenvibration throughout the entire 'corrugated area of thechamber and avoid localized stresses in the region of the nondeformableportion.

21. A pressure sensitive element comprising a sealed chamber, abellows-like flexible member forming a deformable lower portion of saidchamberand adapted to 'change its shape in response to variations inpressure on opposite sides thereof, a hollow non-flexible member forminga nondeformable upper portion of said chamber, a body of liquid in thedeformable portion, `the level of the liquid being'above the uppermostfold :of

'. the bellows-like member to thereby^ dampen vibration throughout theentire wall area oi said deformable portion, said upper portion having aspace therein above the liquid level filled with an l inertgas,

22. A sensitive element comprising a sealed chamber, a deformable memberforming the lower portion of said chamber, a non-deformable memberforming the upper portion of said chamber, and a body ofvibration-damping liquid completely lling the deformable portion butonly partially filling the entire chamber, the chamber containing aninert gas above the liquid.

23. A sensitive element comprising a tubular bellows, means for closingthe ends' of said bellows and forming therewith a sealed chamber, andmeans forming a longitudinally slidable universal connection within thechamber between said closlng means including a guide member carried byone o f said means and a plunger carried .by the other of saidmeans andslidable in said guide member to damp vibrationsoi the bellows.

A24. A sensitive element comprising a tubular bellows, means for closingthe ends of said'bellows. and a dashpot 'for damping vibrations in thebel' ber closing one end of said cylinder, a'relatively movable memberclosing the other end of said cylinder, and means for damping vibrationsin said corrugated cylinder including a body of liquid therein, and acylindrical member extending from one of said closing members into saidcylinder closely adiacent the corrugated wall thereof, theclearancebetween the cylindrical member` and the wall being less than thedistance between the inner surfaces of the transversely extending wallsof the corrugations, to thereby restrict the iiow oiV liquid into or outof the corrugations.

28. A pressure sensitive device comprising a. sealed chamber having tworelatively movable walls adapted to respond to variations in pressure onthe inside and outside of the chamber, means for rigidly mounting one ofsaid walls, a"

lows, said dashpot including a cylinder member carried by one of saidmeans and lying inside oiy the bellows, and a plunger member carried bythe other of said means and slidably engagingv said cylinder member. v

25.'The invention defined in.clalm 24 wherein said `dashpotincludes auniversal' connection to permit misalinement of said closing means '26.Asensitive .element comprising a tubular bellows, a base member closingone end of said bellows, a relatively movable member closing theopposite end of'said bellows, a body of liquid in.

said bellows to damp vibrations thereof, a-control element, and means.forming-a universal con-1 lnection between said control element and"said movable member.I

27.. A pressure-responsive 'device comprising a hollow corrugatedmetallic cylinder, 'a fixed memsaid walls, said bellows and cylinderadapted to contain liquid, and means forming a restricted communicationbetween the inside and outside of `said cylinder.

29. The invention deiined in claim 28 wherein the connection between thepiston and the other of said walls includes'a universal connection.

30. A pressure sensitive device comprising a sealed chamber having tworelatively movable walls responsive to variations in the pressureswithin and outside of said chamber, means for rigidly mounting one ofsaid walls, and means for damping relative vibration of said wallscomprising a dashpot cylinder carried by one of said walls, and a pistonin the cylinder connected to the other o f said walls.

31. A pressure sensitive control unit comprising a corrugated bellows, amember closing one end of said bellows, a second'member closing theother end of the bellows including a cup-like por- Y' tion extendingwithin the bellows, a recess )n one of said members forming a guideportion, a projection from the other of said members having an enlargedrounded end slidably received within the guide portion, means forrigidly mounting one of said members, and a control element abuttingagainst the other of said members to be actuated thereby.

32. A pressure sensitive control unit comprising a housing, a corrugatedbellowsJwithin the housing, a member closing one endof said bellows andsecured to one portion of the housing, a recess in said .member forminga guide portion, a member closing the other end of the bellows includinga cup-like portion extending within the bellows and having a projectionslidably received within the guide portion, a projection from'vanoppositely disposedY portion of the housing in slidable relation withthe cup-like portion, a central bore in said last-named projection, anda control element in said bore in abutting relation with the base ofsaid cup-like portion.

33. A pressure sensitive control unit comprising a housing including abase and a cover, a corrugated bellows within the housing, a`memberclosing one end of the bellows and secured `to the cover, a recessin the member forming a guide portion. a second member closing the othery ,end of the bellows and havingv a cup-like' portion tion, va. pair ofopposit'cly extending within the bellows. guide extending from thesecond member andhaving an enlarged rounded end slidably received'in theguide porextending vcentral projections from the base oi' the housing,one of said projections extending. within the said cuplike portion inslidable 'relation therewith and the other being threaded, a centralbore in said projections. and a control element in said bore extendinginto the cup-like portion and engaging the bottom thereof. p s

34. A pressure responsive ldevice comprising a corrugated metalliccylinder, a rigid cylindrical member coaxial with the cylinder andhaving its walls closely adjacent the corrugated walls ot the cylinder,means including the cylinder and the cylindricall member forming asealed chamber, and means for damping vibrations in the corrug'atcdcylinder including a body of liquidrin the chamber, the clearancebetween the cylindrical member and the corrugated wall of the in said'owpassage to accelerate circulatiom of cylinder being less than thedistance between the inner surfaces oi' the transversely extending wallsoi the corrugations to 'thereby restrict the flow of liquid into or-outof the corrugations.

35. Afdensity-responsive device comprising a sealed chamber denned inpart by' a deformable wall and in part by a non-deformable wall, thatportion of the chamber having a deformable wall containing a dampingliquid functioning to prevent localized vibration stresses, and an inerttemperature-responsive gas replacing air in said chamber above saidliquid, said gas providing aV responsive gas filling the remainder ofthe chamber, said gas being of an inert type having a low amnity for anda low factor of solubility in the damping liquid whereby the gas contentof the device will remain constant over long periods of time to therebyprovidel lasting temperature calibration oi the device.

37. A density-responsive device adapted to control the quantityd offluid flowing through a passage in response tovariations in pressure andtemperature' of air iiowing .through another passage. comprising asealed corrugated bellows filled inpartwithadamplnguidandinpartwithan 10named passage for controlling the latter, and a conduit communicating atits inlet end with said iiow passage and at its outlet end projectinginto said second-named passage, air flowing past the outlet end of saidconduit providing a draft effect air therethrough and quicken responseof the bellows to variations in temperature and-pressure of air insaidsecond-named passage.

38. A density-responsive device adapted to control the quantity of iluidflowing vthrough a passage in response to variations in temperatures andpressure of air flowing through another e, comprising a sealedcorrugated bellows filled in part with a damping fluid and in part withan inert temperature-responsivegas, asupport for Isaid bellows adaptedto be flxed to a member adjacent said second-named passage, a housinghaving air intake and discharge ports therein projecting from saidsupportandextending ad- 80 jacent said bellows and providing inconjunction with the latter a restrictedifi'ow passage for flowing airpast the bellows, one end of said bellows being held iixed with respectto its supportand the opposite end of said bellows being free for $5movement with respect to said support, a conl trol element operativelyconnected to -the movable end of the bellows and projecting intosaidilrstfnamed passage for controlling, flow of iluid through the latter, aprotective shell enclosing at 40 least the upper portion of saidhousing, and .a'

conduit communicating at its inlet end with said flow passage throughsaid shell and' at its discharge end projecting into saidA second-namedpassage in a 'manner'such as to protide an ejector action with respectto said flow passage and expedite circulation .of air between thebellows and` housing.

FRANK c. Mocx.

